Switch



Sept. 10, 1946. E. G. MILLER ETAL SWITCH Filed March 14, 1944 INNTORS W I TQRNEY Patented Sept. 10, 194

UNITED STATES PATENT OFFICE SWITCH Application March 14, 1944, Serial No. 5426,377

2 Claims.

This invention relates to switches and more especially to switches for use in electrical appliances for airplanes.

As is well known, the pressure within an airplane varies to a considerable extent dependent upon the elevation at which the plane is flown. At certain pressures below normal surface level atmospheric pressure, sparking between contacts is materially increased. Thus, a switch which operates without appreciable sparking between its contacts at ground level will be characterized by considerable sparking between the contacts at elevations normally attained by airplanes.

An object of this invention is a switch having provision for satisfactorily suppressing arcing between the contacts when the switch is carried by an airplane to high elevations.

A further object of this invention is a switch which may safety be used in an atmosphere containing explosive vapors or gases.

A still further object of this invention is a mounting for two relatively movable contacts oi' such nature that the atmosphere surrounding the contacts is maintained of the same composition and at substantially uniform pressure.

In one type of switch embodying the invention, a pair of relatively movable contacts are arranged within an air-tight ilexible wall chamber and a suitable gas, for example, air, nitrogen, etc., is provided within the container at pressure which will satisfactorily suppress arcing between the contacts. Means are provided for effecting relative movementI of the contacts toward and away from each other. The chamber is so mounted in the switch that at atmospheric pressure it is under slight compression tending to maintain the maximum gap permissible between the two contacts. Thus, irrespective of the elevation to which the switch is carried, the pressure of the atmosphere surrounding the contacts Fig. 2 is a view similar to Fig. l with the switch in closed condition, and

Fig. 3 is a section on the line 3-3 of Fig. l.

A box-like casing i of insulating material is provided with a removable cover Ii attached to the casing by fasteners i2. In the bottom of the casing lil are two apertures I3 through each of which extends a threaded binding post Id having a head i5 co-nstituting a Contact. The binding post ifi is hermetically sealed in a glass bead i5 which in turn is hermetically sealed in the bore of a metal bush il'. The assembly just described is a commercial product obtainable on the open market.

A metal member il has an aperture through which the binding post extends and a nut i9 threaded onto the end of the bolt iii holds the binding post with the bush il engaging the inner surface oi the casing bottom and the member i3 engaging the outer surface of the casing bottom. A Sylphon bellows Eil of either metallic or non-metallic flexible material has one end hermetically sealed to the bush il and its other end hermetically sealed to a metal plate 2l supporting a Contact 22. The flexible wall chamber thus formed may contain an arc suppressing atmosphere or may be evacuated to a degree sufcient satisfactorily to suppress arcing.

A metal bridge member 23 contacts each of the plates 2| and is provided with a central depression 24 between which and the bottom of the casing is arranged a spring 25. A pin 2S is slidably mounted in a frame 2l with one end engaging the portion 24 of the bridge 23 and with the other end enlarged to form a head 28 engageable with the frame 2l to limit downward movement of the pin. A leaf spring 29 is carried by a bracket 3b attached to the wall of the casing in by a screw 3| and engages the head 28. A cradle 32 is pivotally supported by a shaft 33 journalled in the legs of a U-shaped member 42 supported by the side walls of the housing li] and having its bight portion extending between the lower surface of the frame 2 and the upper surface of the depression 24 in the bridge member 25, there being an aperture in said bight portion for the pin 25 to project through. The relationship of the U member bight to the bellows members 2i) is such that when the bellows members are assembled in the switch at surface level atmospheric pressure the bellows 2i! are slightly compressed. A block of insulating material 34 likewise is pivotally supported by the shaft 33 and is provided with an operating handle 35 extending through an aperture 36 in the cover H.

asevera A plunger extends through an aperture in the cradle 32 and is provided with a head 33 pivoted to the block ill in a recess Z'lil provided in the block by means of a pin All. A spring 4l surrounds the plunger' Eil with one end abutting the head 3B and the other end abutting the end wall oi" the cradle. The cradle Si and the parts associated therewith directly overlie the spring 2S.

In Fig. 1, the parts are shown with the switch in its open condition. The spring .'l rests against the head 2d and the pin 2d together with the bridge ZS and contacts are held in elevated position by the spring and the expansive for-ee of the bellows Clockwise rotation of the block 3a by operation or the handle lifts the pivot pin lil to reverse the position of the plunger il rela tive to horizontal with the result that the cradle 32 is rocked countercloclrwise from the posi' ion shown in Fig. l to the position shown in The left end or the spring is thereupon downwardly to apply pressure to the bead iii of the pin 2:5 thereby forcing the bridge and con tacts downwardly against the action oit the spring 25 into engagement with the contacts it to close a circuit between the two binding posts lil. The switch remains closed so long as handlA Elli is lett its lig. 2 position.. Upon counterclocirwise movement of he the switch returns to the position In the event that the flexible che`I tains an arcsuppressing atmosphe tacts thereiore remains constant irrespective of the pressure surrounding the casing lil. Sparking between the contacts is thus satisfactoriiy suppressed irrespective of the elevation at which the switch may be operated, Also, the switch may be made use of in an atmosphere containing explosive mixture as any sparks that may be generated upon opening of the contacts are retained within the chamber,

We claim:

1. A switch comprising a contact bridging mernber arranged for rectilinear movement, a stop, resilient means biasing said bridging member toe ward said stop7 a pivotally supported hollow rocker, a reoiprocable pin havin-g one end engaging bridging member, a leaf spring xed at one end and extending across the remaining end of said pin in position to be engaged by said rocker, an oscillating member within said rocker coaxial therewith7 a stud pivoted at one end to oscillatable member and extending through f aperture in said rocker, a shoulder on said stud and a resilient member interposed between said shoulder rocker, pin being eiective upon operation of :aid oscillatable member to move said bridgig me er away from said Stop.

A switch according to claim l characterized by a pair oi' airtight chambers each compristwo rigid metal end members interconnected by a metal bellows member, means supporting said c* nibers with one end member of each chamber ai and the other end member capable ci :novernent toward and away from fixed end meinn ber and arranged for engagement by said bridging member, a contact supported by each member ci" a chamber within said chamber with one Contact of each chamber insulated from its sup porting member, and a conductor leading through each stationary end member to the Contact supported thereby.

ED'WARD G. MILLER. RALPH E. ENGBERG. 

